Abstract: Thoroughly exploring the power operation interval control strategy of flexible DC transmission systems is crucial for improving the quality of power transmission and ensuring system stability. In this context,this paper proposes a power operation interval control method for flexible DC transmission system under low short-circuit ratio. Firstly, the power operation characteristics and influencing factors of the flexible DC system under the condition of low short-circuit ratio are analyzed,and the constraints that limit the steady-state operation area of the flexible DC transmission of the modular multilevel converterhigh voltage direct current（MMC-HVDC） are determined.Secondly,based on these constraints,a theoretical calculation model of the power operation interval of the flexible DC transmission system under low short-circuit ratio is constructed,and the calculation program of the power operating range of the flexible system connected by the flexible DC system with low short-circuit ratio and the weak AC system is developed. Finally,the boundary of the steady-state operation region of MMC on the PQ plane is drawn by using the point-by-point scanning method and the implicit function plotting method in the simulation environment to mutually the accuracy of the calculation results and verify the effectiveness of the proposed control method.